Process and apparatus for vapor compression distillation using plate and frame heat exchanger

Abstract

An improved process and apparatus for vapor compression distillation is provided comprising a heat exchanger, a vapor compressor, and a liquid-vapor separator. The heat exchanger is preferably of the plate and frame type, with the plate faces being spaced apart to allow for the microscopic movement of the plates during the distillation process. This movement aids in the breaking off of hard scale which has accumulated on the plates. The process involves passing pressurized vapor and liquid into the heat exchanger, the pressurized vapor condensing to form a distillate, the liquid being heated to form a heated liquid and a non-pressurized vapor, the heated liquid and non-pressurized vapor being passed into a liquid-vapor separator where they are separated, the heated liquid being passed back into the heat exchanger and the non-pressurized vapor being passed into a vapor compressor for passage back into the heat exchanger.

That which is claimed: 
     
       1. A vapor compression distillation apparatus comprising: a heat exchanger;   a vapor compressor being in one-way fluid communication with said heat exchanger;   a liquid-vapor separator being in two-way fluid communication with said heat exchanger and being in one-way fluid communication with said vapor compressor;   an inlet passage for passing feed into said separator; and   a first exit passage for passing distillate out of said heat exchanger;   whereby a pressurized vapor from said vapor compressor and a liquid from said separator can be passed into said heat exchanger such that: said pressurized vapor at least partially condenses and forms a distillate, said distillate being passed out of said heat exchanger through said first exit passage;   said pressurized vapor provides heat to said liquid resulting in the formation of a heated liquid and a non-pressurized vapor, wherein said non-pressurized vapor and said heated liquid can be passed into said separator where they are separated, wherein said non-pressurized vapor can be passed into said vapor compressor for passage back into said heat exchanger, and wherein said heated liquid can be passed back into said heat exchanger.     
     
     
       2. The apparatus according to claim 1 wherein said heat exchanger comprises a plurality of generally vertical plates. 
     
     
       3. The apparatus according to claim 2 wherein faces of adjacent plates are spaced apart for allowing said plates to microscopically move due to thermal and mechanical forces applied to said plates. 
     
     
       4. The apparatus according to claim 3 wherein each said plate further comprises a recessed face and a non-recessed face, and further comprising a gasket attached to said recessed face of each said plate, said gaskets protruding from said recessed faces such that, when said plate pack is compressed, said gaskets will be in contact with said recessed face of one plate and said non-recessed face of an adjacent plate. 
     
     
       5. The apparatus according to claim 2 wherein each of said plates has a middle section comprising a plurality of grooves therein, said plurality of grooves being generally arranged in a chevron configuration, said plates being arranged such that said chevron configurations of adjacent plates point in opposite directions. 
     
     
       6. The apparatus according to claim 2 wherein said plates have generally smooth faces. 
     
     
       7. The apparatus according to claim 2 wherein said plates are made from metal and are coated with Teflon™. 
     
     
       8. The apparatus according to claim 2 wherein said plates are made from a thermoplastic. 
     
     
       9. The apparatus according to claim 1 wherein said two-way communication between said separator and said heat exchanger further comprises a second exit passage communicating with an upper area of said heat exchanger and a middle area of said separator for passing said heated liquid and said non-pressurized vapor into said separator, said second exit passage extending into said middle area of said separator at a downward angle for creating a hurricane-like swirl of liquid in a lower area of said separator, and wherein said separator further comprises a bottom section which is generally shaped as an inverted dome, said hurricane-like swirl sweeping solids toward a center of said bottom section. 
     
     
       10. The apparatus according to claim 9 wherein liquid is maintained at a predetermined level in said separator, said predetermined liquid level being below an outlet of said second exit passage, said hurricane-like swirl for swirling liquid exiting said second exit passage and for swirling liquid in said lower area of said separator. 
     
     
       11. The apparatus according to claim 9 further comprising a concentrate discharge line communicating with said bottom section of said separator for removing concentrate from said separator. 
     
     
       12. The apparatus according to claim 1 wherein said non-pressurized vapor is formed in an upper portion of said heat exchanger. 
     
     
       13. The apparatus according to claim 1 wherein said pressurized vapor enters said vapor compressor at approximately 290° F., and wherein said liquid enters said heat exchanger at approximately 212° F. 
     
     
       14. The apparatus according to claim 1 further comprising a feed pre-heater communicating with said separator and with said heat exchanger, said distillate being passed to said pre-heater through said first exit passage, said distillate providing heat to said feed liquid in said pre-heater, said heated feed liquid being passed from said pre-heater to said separator. 
     
     
       15. The apparatus according to claim 14 further comprising a de-gasser communicating with said pre-heater, said de-gasser for separating desired and undesired types of liquids, any said undesired liquids being removed from said de-gasser and said desired feed liquid being passed from said de-gasser to said separator. 
     
     
       16. A vapor compression distillation process comprising the steps of: providing a heat exchanger, a liquid-vapor separator, and a vapor compressor;   passing a pressurized vapor into said heat exchanger;   passing a liquid into said heat exchanger;   allowing said pressurized vapor to at least partially condense and form a distillate;   passing said distillate out of said heat exchanger;   heating said liquid with heat given off by said pressurized vapor;   forming a heated liquid and a non-pressurized vapor from said liquid;   passing said heated liquid and said non-pressurized vapor into said separator;   separating said heated liquid and said non-pressurized vapor in said separator;   passing said heated liquid into said heat exchanger;   passing said non-pressurized vapor into said vapor compressor;   pressurizing said non-pressurized vapor to form more pressurized vapor; and   passing said more pressurized vapor into said heat exchanger.   
     
     
       17. The process according to claim 16 wherein said step of providing a heat exchanger further comprises providing a heat exchanger comprising a plurality of generally vertical plates, and further comprising the steps of passing said pressurized vapor generally downward through alternate channels between said adjacent plates and passing said liquid generally upward through alternate channels between said adjacent plates such that said pressurized vapor and said liquid generally do not come into direct contact. 
     
     
       18. The process according to claim 16 wherein said step of forming a heated liquid and a non-pressurized vapor from said liquid further comprises forming a heated liquid and a non-pressurized vapor from said liquid in an upper portion of said heat exchanger. 
     
     
       19. The process according to claim 16 further comprising the step of passing solids into said heat exchanger. 
     
     
       20. The process according to claim 16 wherein said step of passing said heated liquid and said non-pressurized vapor into a liquid-vapor separator further comprises passing said heated liquid and said non-pressurized vapor into a liquid-vapor separator at a downward angle, and further comprising the step of swirling liquid in said separator in a hurricane-like motion for sweeping solids to a bottom center of said separator. 
     
     
       21. The process according to claim 20 further comprising the step of periodically passing said solids out of said separator. 
     
     
       22. The process according to claim 16 further comprising the steps of passing a feed liquid into a feed pre-heater, passing said distillate into said pre-heater, allowing said distillate to give off heat in said pre-heater, heating said feed liquid with said heat given off by said distillate.